Think you're safe from allergic reactions inside when pollen counts are high outside?

You won't be if your allergies are triggered by indoor allergens. Most households harbor many allergens that cause sneezing, coughing, itching and wheezing in people sensitive to them. An allergy is a reaction by the body's immune system to a foreign substance, says the Cleveland Clinic. Although most people don't react to normally harmless substances such as dust mites, animal dander and mold, in certain people the immune system treats these substances as invaders.

Dust and dust mites

Dust is a major indoor allergen because it contains many microscopic materials and substances that cause sensitivity in some people. Dust can contain tiny fibers from fabric, animal dander, bacteria, mold spores, bits of food and plants, as well as dust mites, the Cleveland Clinic says.

Dust mites are tiny organisms that live in dust and in fibers found in the home that aren't often washed. You typically find dust mites in bed linens, mattresses, carpeting and fabric-covered furniture, such as sofas. Dust mites excrete waste products that cause an allergic reaction in many people.

The American Academy of Allergy, Asthma and Immunology (AAAAI) offers these suggestions to control dust:

Wash sheets and blankets once a week in hot water and try to decrease bedroom clutter, such as throw pillows and stuffed animals.

Hang vertical window blinds instead of fabrics and draperies, at least in the bedroom, and dust hard surfaces with a damp cloth.

Mold

Molds are microscopic fungi that release spores into the air. Indoor mold can be found wherever it's damp: the bathroom, basement, windowsills and around plumbing. Mold and mildew float through the air, then land and grow in moist areas.

To reduce mold:

If you live in a humid climate, or have a damp basement or other high-humidity room, use a dehumidifier.

Wash and dry hard surfaces, such as tile and countertops, to prevent and remove mold. Use bleach (if it doesn't irritate you) to scour the bathroom.

Replace moldy ceiling tiles and carpet.

Fix leaky plumbing, showers and tubs.

Open windows or use exhaust fans when cooking and showering.

Discard or recycle old newspapers, books, clothing and bedding.

Limit the number of houseplants to reduce mold indoors.

Pet dander

Allergies to pets are usually allergies to the proteins found in skin cells shed by pets and the proteins found in the pet's saliva. You may not notice a pet allergy when you first get a pet. It may develop over a year or two. Once you develop allergic symptoms, they may continue for a period even after you no longer have the pet.

Some patients who are dust mite sensitive but are not allergic to their dog or cat will have worse symptoms because of increased dust mite prevalence, since mites eat animal as well as human scales. So- if you are dust mite sensitive, keep your pet out of the bedroom even if you do not have animal sensitivity on allergy tests.

To reduce pet dander:

Use a HEPA filter, especially in the bedroom.

Keep pets outdoors whenever possible, and definitely out of the bedroom. Bathe them once a week.

Ask a family member who doesn't have pet allergies to brush your cat or dog outside and clean the litter box.

Beyond prevention

If your allergy symptoms persist, talk with your doctor about other ways to ease life indoors. Medications, including nasal sprays or allergy shots, can help treat symptoms, especially if you take steps to reduce allergens in your home.